Softer than soft: diving into squishy granular matter

TL;DR

This paper explores squishy granular matter, a highly deformable material with grains that change shape significantly without breaking, highlighting the challenges in studying such systems experimentally and numerically.

Contribution

It provides a comprehensive definition of squishy granular systems and summarizes the key challenges in their experimental, numerical, and analytical study.

Findings

Defines squishy granular matter and its characteristics.

Identifies major challenges in studying deformable granular systems.

Highlights the need for diverse rheology and large deformation analysis.

Abstract

Softer than soft, squishy granular matter is composed of grains capable of significantly changing their shape (typically larger than 10% of deformation) without tearing or breaking. Because of the difficulty to test these materials experimentally and numerically, such a family of discrete systems remains largely ignored in the granular matter physics field despite being commonly found in nature and industry. Either from a numerical, experimental, or analytical point of view, the study of highly deformable granular matter involves several challenges covering, for instance: ($i$) the need to include a large diversity of grain rheology, ($ii$) the need to consider \dc{large material} deformations, and ($iii$) the analysis upon the effects the large body distortion has on the global scale. In this article, we propose a thorough definition of these squishy granular systems, and we summarize the upcoming challenges in their study.